Microbiome Bacteria Trigger Heritable Immune Defense Against Intracellular Pathogens in C. elegans
Researchers have identified a natural gut bacterium, Stenotrophomonas indicatrix JUb19, that activates an immune defense program in C. elegans against intracellular pathogens without infection being present. The bacterium achieves this through single-stranded RNA signals that trigger the worm's Intracellular Pathogen Response alongside broad metabolic changes. Notably, this protection is inherited by offspring who were never exposed to the bacterium, revealing a transgenerational immune priming mechanism.
A study published on bioRxiv reports that Stenotrophomonas indicatrix JUb19, a natural member of the C. elegans gut microbiome, can partially activate the host's Intracellular Pathogen Response (IPR) even in the absence of active infection. The researchers identified bacterial single-stranded RNA as the molecular signal responsible for this immune activation, representing a newly described class of microbiome-derived cue that links microbial colonization to host defense. Worms exposed to JUb19 showed reduced susceptibility to both viral and microsporidian pathogens, demonstrating broad-spectrum protection against intracellular threats. Crucially, this protection was transmitted to unexposed progeny, indicating an epigenetic or RNA-based transgenerational inheritance mechanism. However, the immune activation comes at a measurable fitness cost to the parental generation, suggesting an evolutionary trade-off between defense and reproductive or metabolic performance. The findings expand understanding of how the microbiome can proactively shape host immunity rather than merely responding to infection.
What's missing
The study does not clarify the precise molecular mechanism by which protection is inherited across generations (e.g., whether small RNAs, chromatin modifications, or other epigenetic marks are responsible). It also remains unknown whether analogous microbiome-derived RNA signals operate in mammals or other organisms.
What different sources said
- bioRxivCenter
Microbiome-Derived RNA Promotes Heritable Defense Against Intracellular Pathogens in Caenorhabditis elegans
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